Project Summary The parent grant is developing microneedle patch (MNP) technology to access interstitial fluid (ISF) of the skin, which can be used to assay proteins produced by Mycobacterium tuberculosis (Mtb) bacteria and, in that way, enable differential diagnosis of people with early- or late-stage active infection, latent tuberculosis infection and cleared infection or BCG vaccination using a low-cost, simple-to-administer and rapid test. In addition to Mtb proteins, ISF contains other biomarkers of interest to research and future medical applications, as shown by recent work by us and others. However, ISF is difficult to collect, currently requiring methods that are cumbersome, costly, invasive and/or time consuming. Therefore, in this Administrative Supplement, we will develop a device for ISF collection that is easy to use and readily accessible to researchers interested in collecting and studying ISF. To accomplish this we have two Specific Aims. Aim I is to develop a small, Wearable ISF Collection Kit (WICK) containing microneedles, suction-mediated ISF flow and an ISF reservoir. We will combine MNP technology developed in our lab to create micropores in skin through which ISF can flow with a device developed by another group that applies suction to the skin at the site of the micropores to withdraw ISF and collect it in a reservoir for subsequent analysis. This modified ISF collection device (i.e., WICK) will be simple-to-operate and deployable in the lab and in the field, thereby enabling many researchers to collect and study ISF biomarkers. In Aim II we will assess the ability of WICK to collect ISF from skin in human subjects. Using WICK, we will study the pharmacokinetics of caffeine, a model drug, in ISF and plasma in 10 human subjects. This will enable initial assessment of WICK to collect ISF in humans. We expect that this project will provide (i) a device (i.e., WICK) for simple-to-operate collection of ISF from animals and human subjects, (ii) studies demonstrating the capabilities of WICK to collect ISF from animals and human subjects and (iii) the basis for future collaboration with multiple research groups to access ISF to assay biomarkers of interest.